Method and apparatus for producing salt water-mixed sherbet ice

ABSTRACT

Salt water fed to an ice-maker  1  is cooled to generate ice. The ice is scraped by scrapers  1   c  to form small particles of ice which are mixed with the salt water to generate salt water-mixed sherbet ice  143 . The salt water-mixed sherbet ice is fed from the ice-maker to an ice storage tank  14  so as to be stored in the ice storage tank. A predetermined amount of the salt water-mixed sherbet ice with a predetermined sherbet concentration at a predetermined low temperature is stored in the ice storage tank while the salt water-mixed sherbet ice is refluxed from the ice storage tank to the ice-maker. Water  24  is injected into the salt water-mixed sherbet ice in the process of producing the salt water-mixed sherbet ice. By the method of producing salt water-mixed sherbet ice, salt water-mixed sherbet ice at a relatively high temperature can be produced easily.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for producing salt water-mixed sherbet ice, in which ice generated by cooling so-called salt water such as sea water supplied is scraped as small particles of ice by a scraper to thereby produce salt water-mixed sherbet ice having the small particles of ice mixed with the salt water.

2. Description of the Background Art

Sea fishes were heretofore generally cooled with blocks of ice to keep freshness of the sea fishes. However, the sea fishes might be damaged by the blocks of ice because of vibration during marine and land transportation when the blocks of ice were ordinary blocks of ice or the freshness of the sea fishes might be lost by water generated by melting the blocks of ice. Therefore, in recent years, a method in which ice generated by cooling salt water is formed into sherbet-shaped or power snow-shaped ice mixed with salt water (hereinafter referred to as salt water-mixed sherbet ice) by a scraper (also called scraping machine or scraping blade) so that sea fishes are cooled with the salt water-mixed sherbet ice, has been used as disclosed in Patent Document 1.

It has been recently found that the temperature of salt water-mixed sherbet ice for keeping the freshness and taste of sea fishes varies according to the kind of fish when the sea fishes are cooled with the salt water-mixed sherbet ice. For example, when sea fishes are cooled with salt water-mixed sherbet ice at −3° C., there is a possibility that a bad influence such as freezing of fish meat or clouding of fish eyes may occur according to the kind and size of fish.

For example, when salt water-mixed sherbet ice with an ice concentration (percent by weight of small particles of ice to the salt water-mixed sherbet ice, also called ice packing factor (IPF)) of 30% is produced from general sea water (with a salt concentration of about 3.5%), the temperature of the salt water-mixed sherbet ice is −3.1° C. When the salt water-mixed sherbet ice at this temperature is used for cooling fishes, fish meat of almost fishes is however frozen so that the commercial value thereof is lost. It is therefore necessary to adjust the salt concentration in order to provide salt water-mixed sherbet ice at such a temperature that fish meat is not frozen. For example, it is necessary to prepare salt water at a salt concentration of 1.7% in order to produce salt water-mixed sherbet ice with an ice concentration of 30% at −1.5° C. (Refer to Patent Document 1 for the relation between the salt concentration and the temperature of salt water-mixed sherbet ice, though there is no description about the relation between the ice concentration and the temperature of salt water-mixed sherbet ice.)

When salt water with a low salt concentration, for example, a salt concentration of about 1.5% is used, ice produced by an ice-maker becomes so hard that there arises a problem that a scraper of the ice-maker is worn severely and motive power for driving the scraper becomes very large. Therefore, an attempt to use ocean deep water (sea water 200 m or more below sea level) for performing supercooling and canceling of supercooling has been made (see Patent Document 2).

[Patent Document 1] JP-A-2002-115945 (FIG. 1 and paragraph number 0035)

[Patent Document 2] JP-A-2006-10129 (FIGS. 1 to 3 and description thereof)

If sea water with a low salt concentration (e.g. of 1.5%) is used for producing salt water-mixed sherbet ice at a relatively high temperature (e.g. of −1.5° C.) as in Patent Document 1, there arises a problem that the scraper of the ice-maker is worn severely and motive power for driving the scraper becomes very large. It is therefore preferable that salt water-mixed sherbet ice at a relatively high temperature (e.g. of −1.5° C.) can be produced without use of sea water having a low salt concentration.

Although Patent Document 2 has described that ocean deep water (sea water 200 m or more below sea level) is used for performing supercooling and canceling of supercooling, it is difficult to produce salt water-mixed sherbet ice stably by such a method for performing supercooling and canceling of supercooling. It is therefore preferable that salt water-mixed sherbet ice at a relatively high temperature (e.g. of −1.5° C.) can be produced without use of such a method and with use of unexceptional sea water or easily available salt water.

SUMMARY OF THE INVENTION

In consideration of the aforementioned circumstances, an object of the present invention is to provide a method and apparatus for producing salt water-mixed sherbet ice at a relatively high temperature (e.g. of −1.5° C.) easily.

The present invention provides a method of producing salt water-mixed sherbet ice, including the steps of: generating salt water-mixed sherbet ice by cooling salt water fed to an ice-maker to generate ice, scraping the ice by scrapers to form small particles of ice to thereby mix the small particles of ice with the salt water; feeding the salt water-mixed sherbet ice from the ice-maker into an ice storage tank to thereby store the salt water-mixed sherbet ice in the ice storage tank; and storing a predetermined amount of the salt water-mixed sherbet ice with a predetermined sherbet concentration at a predetermined low temperature in the ice storage tank while the salt water-mixed sherbet ice stored in the ice storage tank is refluxed from the ice storage tank to the ice-maker repeatedly a plurality of times; wherein water is injected into the salt water-mixed sherbet ice in the process of producing salt water-mixed sherbet ice. Accordingly, there is an effect that salt water-mixed sherbet ice at a relatively high temperature can be produced easily.

This invention also provides an apparatus of producing salt water-mixed sherbet ice, including: an ice-maker which generates salt water-mixed sherbet ice under control based on a controller in such a manner that ice generated by cooling salt water fed to the ice-maker is scraped by scrapers to form small particles of ice to thereby mix the small particles of ice with the salt water; an ice storage tank which stores the salt water-mixed sherbet ice fed from the ice-maker under control based on the controller; and a water injecting unit which injects water into the salt water-mixed sherbet ice; wherein control is performed by the controller so that the salt water-mixed sherbet ice stored in the ice storage tank is refluxed from the ice storage tank to the ice-maker and the injection of water is performed by the water injecting unit in steps of feeding the salt water-mixed sherbet ice from the ice-maker to the ice storage tank and refluxing the salt water-mixed sherbet ice from the ice storage tank to the ice-maker. Accordingly, there can be achieved a salt water-mixed sherbet ice producing apparatus which can produce salt water-mixed sherbet ice at a relatively high temperature easily.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing Embodiment 1 of this invention and showing an example of overall system configuration of a salt water-mixed sherbet ice producing apparatus for carrying out a salt water-mixed sherbet ice producing method;

FIG. 2 is a flow chart showing Embodiment 1 of this invention and showing an example of a salt water-mixed sherbet ice producing sequence in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 1;

FIG. 3 is a graph showing Embodiment 1 of this invention and showing the relation between salt concentration and freezing point due to the action of freezing-point depression;

FIG. 4 is a graph showing Embodiment 1 of this invention and showing ice-making curves at salt concentrations of 1.0% to 4.5% taken at intervals of 0.5%;

FIG. 5 is a graph showing Embodiment 1 of this invention and showing an example of salt water state and ice-making curve in the case where salt water-mixed sherbet ice is produced in the condition of an initial salt water concentration of 2.5%, a target salt water-mixed sherbet ice temperature of −1.5° C. and a target ice concentration (IPF) of 25% by the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 1;

FIG. 6 is a diagram showing Embodiment 2 of this invention and showing another example of overall system configuration of the salt water-mixed sherbet ice producing apparatus for carrying out the salt water-mixed sherbet ice producing method;

FIG. 7 is a flow chart showing Embodiment 2 of this invention and showing an example of a salt water-mixed sherbet ice producing sequence in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 6;

FIG. 8 is a graph showing Embodiment 2 of this invention and showing an example of salt water state and ice-making curve in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 6;

FIG. 9 is a flow chart showing Embodiment 3 of this invention and showing a further example of a salt water-mixed sherbet ice producing sequence in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus;

FIG. 10 is a graph showing Embodiment 3 of this invention and showing an example of salt water state and ice-making curve in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing sequence shown in FIG. 9;

FIG. 11 is a graph showing an example of salt water state and ice-making curve showing the fact that salt water-mixed sherbet ice can be produced in the condition of a target point range of −1.5° C. to −0.5° C. and an IPF range of 15% to 25% in the case of salt concentration C=3.0 in Embodiment 1 (without any dewatering device) and Embodiment 3 (without any dewatering device) of this invention; and

FIG. 12 is a graph showing an example of salt water state and ice-making curve showing the fact that salt water-mixed sherbet ice can be produced in the condition of a target point range of −1.5° C. to −0.5° C. and an IPF range of 15% to 25% in the case of salt concentration C=3.0 in Embodiment 2 (with a dewatering device) of this invention.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

Embodiment 1 of this invention will be described below with reference to FIGS. 1 to 5. FIG. 1 is a diagram showing an example of overall system configuration of a salt water-mixed sherbet ice producing apparatus for carrying out a salt water-mixed sherbet ice producing method. FIG. 2 is a flow chart showing an example of a salt water-mixed sherbet ice producing sequence in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 1. FIG. 3 is a graph showing the relation between salt concentration and freezing point due to the action of freezing point depression. FIG. 4 is a graph showing ice-making curves at salt concentrations of 1.0% to 4.5% taken at intervals of 0.5%. FIG. 5 is a graph showing an example of salt water state and ice-making curve in the case where salt water-mixed sherbet ice is produced in the condition of an initial salt concentration of 2.5%, a target salt water-mixed sherbet ice temperature of −1.5° C. and a target ice concentration (IPF) of 25% by the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 1.

In FIG. 1, the salt water-mixed sherbet ice producing apparatus has: an ice-maker (also called ice generator) 1; a drive source (a motor for driving a rotary cylinder 1 f (which will be described later) in this Embodiment 1) 2 for the ice-maker 1; an ice-maker load detection sensor (a current sensor, an ammeter, etc.) 3 for detecting the load state of the ice-maker 1; a refrigerator 4; a compressor 5; a condenser 6; a cooling medium piping 7; an expansion valve 8; a pressure sensor 9; a temperature sensor 10Ts; a main circulating pump 11; a pump controller 11 a such as an inverter, etc.; a reflux path piping (ice-maker 1←ice storage tank 14 (salt water or salt water-mixed sherbet ice 143 is fed from the ice storage tank 14 to the ice-maker 1 by the main circulating pump 11)) 12; a fresh water temperature sensor 12Tw; a flux path piping (ice-maker→ice storage tank (salt water-mixed sherbet ice 143 is fed from the ice-maker 1 to the ice storage tank 14 by the main circulating pump 11)) 13; the ice storage tank 14 for storing a mixture 143 of sherbet ice and salt water (i.e. salt water-mixed sherbet ice); a salt water-mixed sherbet ice discharging path 141; a drain path 142; a salt water-mixed sherbet ice discharging path switching valve 14 a; a drain path switching valve 14 b; a salt water-mixed sherbet ice storage level sensor 14 cLs for detecting the storage level of salt water-mixed sherbet ice in the ice storage tank 14; a stirrer (also called agitator) 16 driven by a drive source (e.g. a motor) 15; a first valve 19 for the ice storage tank 14; a second valve 21 for the ice storage tank 14; a salt concentration adjusting tank 22; a salt water injection pipe 231 for injecting salt water 23 such as sea water from a salt water source (not shown) into the ice storage tank 14; a fresh water injection pipe 241 for injecting fresh water 24 from a fresh water source (not shown) into the ice storage tank 14; a fresh water amount adjusting valve 25 for controlling the amount of fresh water 24 injected into the ice storage tank 14; a salt concentration sensor 26 cl for detecting the salt concentration C of salt water-mixed sherbet ice 143 in the ice storage tank 14; a cold salt water feed control valve 28 for controlling the amount of cold salt water injected into the ice storage tank 14; and a controller 100 provided with a setting portion 110.

The ice-maker 1 has: a cooling medium side passage 1 a provided with an evaporator function; a salt water side passage 1 b; scrapers (also called scraping machines or scraping blades) 1 c; an outer cylinder 1 d; an inner cylinder 1 e; and the rotary cylinder 1 f. The cooling medium side passage 1 a is formed between the outer cylinder 1 d and the inner cylinder 1 e so that the cooling medium side passage 1 a is shaped like a cylinder. The salt water side passage 1 b is formed between the rotary cylinder 1 f and the inner cylinder 1 e so that the salt water side passage 1 b is shaped like a cylinder. The scrapers 1 c are attached to an outer circumference of the rotary cylinder 1 f at regular intervals both in a circumferential direction and in a direction of extension of a center line so that the scrapers 1 c are disposed in the salt water side passage 1 b.

The salt water-mixed sherbet ice discharging path switching valve 14 a for opening and closing the salt water-mixed sherbet ice discharging path 141 is provided in the salt water-mixed sherbet ice discharging path 141 provided in a side wall of the ice storage tank 14 near the bottom of the ice storage tank 14.

The drain path switching valve 14 b for opening and closing the drain path 142 is provided in the drain path 142 provided in the bottom of the ice storage tank 14.

The salt water-mixed sherbet ice storage level sensor 14 cLs for detecting the storage level of salt water-mixed sherbet ice 143 in the ice storage tank 14 is provided in the ice storage tank 14.

The controller 100 receives detection outputs of the respective sensors 3, 9, 10Ts, 12Tw, 14 cLs and 26 cl and controls the respective drive sources 2 and 15, the refrigerator 4, the respective valves 8, 14 a, 14 b, 19, 21 and 28 and the pump controller 11 a to execute the salt water-mixed sherbet ice producing sequence in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIGS. 2, 5 and 7 which will be described later.

The setting portion 110 in the controller 100 sets a target point, etc. which will be described later.

A salt water feed unit is formed from the salt water source (not shown), the salt water injection pipe 231 and the cold salt water feed control valve 28. A fresh water feed unit is formed from the fresh water source (not shown), the fresh water injection pipe 241 and the fresh water amount adjusting valve 25.

An overall schematic operation of the salt water-mixed sherbet ice producing method and apparatus will be described below with reference to FIG. 1.

When the producing apparatus is powered on so that the controller 100 starts, salt water in the salt water source, for example, with a salt concentration of 2.5%, 3%, 3.5%, etc. selected by a user is injected into the ice storage tank 14 through the cold salt water feed control valve 28 so as to be stored in the ice storage tank 14.

The salt water stored in the ice storage tank 14 is thrown into the salt water side passage 1 b of the ice-maker (ice generator) 1 by the circulating pump 11. A cooling medium liquid at about −12° C. fed from the refrigerator 4 flows in the cooling medium side passage 1 a of the ice-maker 1.

The salt water having the predetermined salt concentration and the predetermined temperature flows in the salt water side passage 1 b of the ice-maker 1 and comes into contact with an inner circumferential surface (heat transmission surface) of the inner cylinder 1 e of the ice-maker 1, so that the salt water in contact with the inner circumferential surface of the inner cylinder 1 e is cooled with the cooling medium in the cooling medium side passage 1 a. In this manner, ice is generated on the inner circumferential surface of the inner cylinder 1 e.

The ice generated on the inner circumferential surface of the inner cylinder 1 e is scraped by the scrapers (scraping blades) 1 c on the outer circumference of the rotary cylinder 1 f which are driven to rotate by the ice-maker drive source (rotary cylinder drive motor) 2.

The ice scraped by the scrapers 1 c is provided as particles with a size of about 0.1 mm. The ice particles float in the salt water in the salt water side passage 1 b of the ice-maker 1 so as to be shaped like sherbet containing salt water. That is, salt water-mixed sherbet ice is generated.

The salt water-mixed sherbet ice generated in the salt water side passage 1 b of the ice-maker 1 is extruded from the salt water side passage 1 b by the circulating pump 11 so as to be fed into the ice storage tank 14 via the flux path piping 13. Thus, the salt water-mixed sherbet ice is stored in the ice storage tank 14.

The salt water-mixed sherbet ice 143 stored in the ice storage tank 14 is refluxed into the salt water side passage 1 b of the ice-maker 1 via the reflux path piping 12 by the circulating pump 11. Thus, ice is generated on the inner circumferential surface of the inner cylinder 1 e in the same manner as described above. The ice is scraped by the scrapers 1 c, so that salt water-mixed sherbet ice containing a large amount of ice particles is generated in the salt water side passage 1 b.

The salt water-mixed sherbet ice containing such an increasing amount of ice particles is further extruded from the salt water side passage 1 b by the circulating pump 11 in the same manner as described above. Thus, the salt water-mixed sherbet ice is fed into the ice storage tank 14 via the flux path piping 13, so that the salt water-mixed sherbet ice is stored in the ice storage tank 14.

The flux and reflex cycle including reflux of salt water-mixed sherbet ice from the ice storage tank 14 into the salt water side passage 1 b, generation of salt water-mixed sherbet ice containing a large amount of ice particles in the salt water side passage 1 b and flux of the salt water-mixed sherbet ice containing a large amount of ice particles from the salt water side passage 1 b into the ice storage tank 14 is repeated many times so that a predetermined amount of salt water-mixed sherbet ice 143 with a predetermined sherbet concentration IPF is stored in the ice storage tank 14.

In this manner, since it is impossible to obtain salt water-mixed sherbet ice 143 with a predetermined sherbet concentration when salt water is passed through the ice-maker 1 once, the flux and reflux cycle is repeated many times to thereby gradually generate salt water-mixed sherbet ice 143 with a predetermined sherbet concentration.

For example, to generate 10 tons of salt water-mixed sherbet ice 143 with a predetermined sherbet concentration of 30%, the flux and reflux cycle is repeated for about 10 hours to thereby gradually generate the salt water-mixed sherbet ice 143. Accordingly, since a large amount of ice cannot be generated in the salt water side passage 1 b of the ice-maker 1 in a short time, the locked state in which the ice-maker cannot operate (the rotary cylinder 1 f cannot rotate) is almost prevented from being caused by aggregation due to solidification of sherbet ice, compared with the method and apparatus according to the background art.

Incidentally, as the flux and reflux cycle is repeated, the sherbet concentration of salt water-mixed sherbet ice increases gradually and the viscosity thereof increases gradually. The gradual increase in the sherbet concentration of salt water-mixed sherbet ice and in the viscosity thereof means that the ice-maker 1 gets close to a state in which the ice-maker 1 is overloaded and to a state in which the ice-maker 1 is locked. Accordingly, although the locked state can be almost prevented in Embodiment 1 of the invention as described above, it is necessary to take measures to prevent the locked state, for example, even when sudden drop in the ambient temperature due to sudden change in the weather, repetition of momentary power failure, etc. occurred, so that a more reliable salt water-mixed sherbet ice producing method and apparatus can be achieved.

When the sherbet concentration of salt water-mixed sherbet ice becomes too high, for example, when the sherbet concentration exceeds 50% and becomes a considerably high value of 60%, 70% or 80%, the viscosity of the salt water-mixed sherbet ice 143 becomes so high that not only does forced circulation of the salt water-mixed sherbet ice into the salt water side passage 1 b of the ice-maker 1 by the circulating pump 11 become difficult but also the drive source (rotary cylinder drive motor) 2 of the ice-maker becomes high-loaded and overloaded successively and stops finally. Therefore, when salt water-mixed sherbet ice with a proper sherbet concentration, for example, with a sherbet concentration of 30% has been generated, the controller 100 stops the refrigerator 4 to stop ice-making so that sherbet ice cannot be produced any more. On this occasion, the judgment in the controller 100 as to whether the proper sherbet concentration is obtained is, for example, based on the temperature of salt water-mixed sherbet ice measured by the temperature sensor 10Ts. That is, when the temperature of salt water-mixed sherbet ice reaches a specified temperature, the refrigerator 4 is stopped. In other words, the proper ice concentration IPF is detected based on the temperature of salt water-mixed sherbet ice corresponding to the salt concentration, so that the operation of the refrigerator 4 is stopped in accordance with detection of the proper ice concentration IPF of salt water-mixed sherbet ice.

In this manner, the temperature of salt water-mixed sherbet ice is monitored to control the operation of the refrigerator 4 so that overloading and stopping of the ice-maker 1 can be prevented from being caused by excess of the sherbet concentration.

Incidentally, the specified temperature depends on the salt concentration of sea water. For example, the specified temperature is −3.1° C. for a salt concentration of 3.5%, and −2.1° C. for a salt concentration of 2.5%. −3.1° C. is lower than −2.1° C. The salt concentration of sea water varies according to environment. For example, the salt concentration becomes low just after a heavy rain or near a river estuary. Accordingly, when the salt concentration is lowered, it is necessary to increase the specified temperature in accordance with a value detected by the salt concentration sensor 26 cl and stop the refrigerator 4 quickly after the sherbet concentration reaches a proper concentration. However, the theory and practice are not always consistent with each other even when the specified temperature is increased because the salt concentration is lowered. That is, salt water-mixed sherbet ice with a higher sherbet concentration than the theoretically estimated value thereof is generated so that the viscosity of the salt water-mixed sherbet ice becomes high. Accordingly, not only does forced circulation of the salt water-mixed sherbet ice into the salt water side passage 1 b of the ice-maker 1 by the circulating pump 11 become difficult, but also the ice-maker drive source (rotary cylinder drive motor) 2 may be stopped because of high load. Moreover, when the sherbet concentration becomes further higher, there is fear that ice in the salt water-mixed sherbet ice in the salt water side passage 1 b of the ice-maker 1 may grow up so that the volume of ice increases to thereby break the body of the ice-maker 1.

Therefore, when the load on the drive source 2 increases, the controller 100 controls the pump controller (inverter) 11 a automatically, in accordance with the output of the ice-maker load detection sensor (current sensor) 3 detecting the load state of the drive source 2 driving the rotary cylinder 1 f of the ice-maker 1, to increase the output of the circulating pump 11, increase the discharging pressure of the circulating pump 11 and forcedly extrude salt water-mixed sherbet ice from the salt water side passage 1 b to the flux path piping 13 at the initial stage of solidification of sherbet ice to thereby present the ice-maker 1 from lapsing into the overload state or the locked state. Incidentally, when the load on the ice-maker 1 reaches a predetermined value or higher, the user may be informed of the overload state through a buzzer, voice, etc. so that the output of the circulating pump 11 can be increased manually when the user is informed of the overload state. Although the cost of the apparatus becomes slightly low when such a manual operation is used, there is fear that the timing to increase the output of the circulating pump 11 may be delayed or the increasing amount of the output of the circulating pump 11 may be small. To prevent such a disadvantage, it is preferable that the circulating pump 11 is controlled automatically by the controller 100.

Under the state in which the flux and reflux cycle is repeated many times by the controller 100, the salt water feed control valve 28 is closed by the controller 100. On the other hand, under the state in which the flux and reflux cycle is repeated many times, when the target ice concentration IPF of the salt water-mixed sherbet ice is, for example, 25%, the temperature of a mixture of sherbet ice and salt water in the salt water side passage 1 b is normally −1.9° C., for example, for a salt concentration of 2.5%. The temperature reaches about −2.7° C. for a salt concentration of 3.5%.

Therefore, in Embodiment 1 of the invention, in addition to the automatic control of the output of the circulating pump 11 based on the output of the ice-maker load detection sensor 3, the output of the temperature sensor 10Ts is used so that automatic control is performed by the controller in such a manner that ice-making is continued until the ice concentration IPF of the salt water-mixed sherbet ice reaches the target value, for example, until the ice concentration IPF reaches 35% when the target ice concentration IPF is 25%; the fresh water amount adjusting valve 25 is opened to feed fresh water 24 from the fresh water injection pipe 241 into the ice storage tank 14 when the temperature detected by the temperature sensor 10Ts reaches −2.3° C. corresponding to the ice concentration IPF of 35%, for example, when the salt concentration C is 2.5%; and the fresh water amount adjusting valve 25 is closed to stop the feed of fresh water 24 into the ice storage tank 14 when the temperature detected by the temperature sensor 10Ts reaches the target value, for example, −1.5° C. In this manner, salt water-mixed sherbet ice at a relatively high temperature (e.g. of −1.5° C.) can be easily produced from salt water having a high salt concentration.

In the method in which ice generated by cooling salt water is scraped by the scrapers 1 c as in the ice-maker 1 in this Embodiment 1, when the salt concentration of the salt water is low, the generated ice cannot be scraped because the generated ice is hard. That is, since it is impossible to scrape ice when salt water having a salt concentration lower than 2.5% is used, it is necessary to use salt water having a salt concentration of 2.5% or higher.

However, when salt water having a salt concentration of 2.5% or higher is used, the temperature at which ice generation starts is −1.5° C., ice is generated as it is, and the temperature at which the ice concentration IPF reaches 30% is −2.1° C. The salt water-mixed sherbet ice at −2.1° C. cannot be applied to cooling of some kind of fish because fish meat may be frozen when the salt water-mixed sherbet ice is applied to cooling of fish.

Therefore, in this Embodiment 1, the output of the temperature sensor 10Ts is used so that automatic control is performed by the controller in such a manner that ice-making is continued until the temperature of the salt water-mixed sherbet ice becomes the target value or higher; the fresh water amount adjusting valve 25 is opened to feed fresh water 24 from the fresh water injection pipe 241 into the ice storage tank 14 when the temperature of the salt water-mixed sherbet ice reaches, for example, −2.3° C.; and the fresh water amount adjusting valve 25 is closed to stop the feed of fresh water 24 into the ice storage tank 14 when the detected temperature of the temperature sensor 10Ts reaches the target value, for example, −1.5° C. In this manner, salt water-mixed sherbet ice at a relatively high temperature (e.g. of −1.5° C.) can be easily produced from salt water having a high salt concentration.

The operation sequence in the controller 100 which is a process of producing salt water-mixed sherbet ice based on ice-making and injection of fresh water will be described below with reference to FIG. 2.

In FIG. 2, first, the finished temperature (target temperature) Ts2 and finished IPF (target IPF (ice concentration)) of salt water-mixed sherbet ice are set in the setting portion 110 of the controller 100 (step ST201).

Then, salt water is injected from the salt water injection pipe 231 into the ice storage tank 14. Further, the salt concentration C of salt water in the ice storage tank 14 is measured by the salt concentration sensor 26 cl and the level (water level) of salt water in the ice storage tank 14 is measured by the salt water-mixed sherbet ice storage level sensor 14 cLs (step ST202).

Then, the ice-making completion temperature Ts1 is set in the setting portion 110 of the controller 100 (step ST203).

Then, the first and second valves 19 and 21 are opened, the main circulating pump 11 is operated and the ice-maker 1 and the refrigerator 4 are operated to perform ice-making (step ST204).

Then, whether or not the temperature Ts of salt water-mixed sherbet ice which is the output of the temperature sensor 10Ts has reached the ice-making completion temperature Ts1 (the set value of which is, for example, about −2.2° C. when the salt concentration C is 2.5%) is judged based on measurement information of the temperature Ts (step ST205).

When a result of the judgment in the step ST205 shows NO (the temperature Ts has not reached the ice-making completion temperature Ts1), ice-making is continued.

On the other hand, when a result of the judgment in the step ST205 shows YES (the temperature Ts has reached the ice-making completion temperature Ts1), ice-making is stopped (step ST206).

The steps ST201 to ST206 are an operation sequence for settings in a standard ice-making function portion 101 of the controller 100. This operation sequence is the same as the operation sequence in steps of the salt water-mixed sherbet ice producing method according to the background art, except the setting of the finished temperature (target temperature) Ts2 of salt water-mixed sherbet ice. In the steps ST201 to ST206, salt water-mixed sherbet ice at a low temperature is generated.

Then, the fresh water amount adjusting valve 25 is opened so that fresh water 24 is injected from the fresh water injection pipe 241 into the ice storage tank 14 (step ST207).

Then, whether or not the temperature Ts of salt water-mixed sherbet ice which is the output of the temperature sensor 10Ts has reached the finished temperature Ts2 (the set value of which is, for example, −1.5° C. when the salt concentration C is. 2.5%) is judged based on measurement information of the temperature Ts (step S208).

When a result of the judgment in the step ST208 shows NO (the temperature Ts has not reached the finished temperature Ts2), injection of fresh water 24 is continued.

On the other hand, when a result of the judgment in the step ST208 shows YES (the temperature Ts has reached the finished temperature Ts2), the fresh water amount adjusting valve 25 is closed to stop injection of fresh water 24 (step S209).

In the step ST209, salt water-mixed sherbet ice at a relatively high temperature, for example, of −1.5° C. as the target value and with an IPF of 25% is finished. The finished salt water-mixed sherbet ice at a relatively high temperature in the ice storage tank 14 is then discharged from the salt water-mixed sherbet ice discharging path 141 automatically or optionally (step ST210).

The steps ST207 to ST209 are an operation sequence in a fresh water injecting function portion 102 of the controller 100. By the steps ST207 to ST209, salt water-mixed sherbet ice at a required relatively high temperature can be produced easily.

Incidentally, the injection of fresh water is performed while the salt water-mixed sherbet ice in the ice storage tank 14 is stirred by the stirrer 16 so that the temperature and IPF of the salt water-mixed sherbet ice are uniformized in the whole region in the ice storage tank 14.

Thermophysical properties of the salt water-mixed sherbet ice will be described below.

The matter that salt water-mixed sherbet ice at a high temperature can be produced when water is mixed with salt water such as sea water as described above will be described below.

First, the freezing temperature of salt water will be described. A salt water NaCl solution is not frozen at 0° C. which is the freezing point of fresh water, but frozen at a point lower than 0° C. because of the action of freezing point depression.

FIG. 3 shows the relation between salt concentration and freezing point due to the action of freezing point depression. When salt water is further cooled after it begins to be frozen, ice is generated so that the amount of ice increases. Moreover, since ice itself is fresh water, the salt concentration of the remaining salt water portion increases gradually. As the salt concentration increases, the freezing point decreases. Accordingly, when ice-making is continued, the amount of ice increases gradually and the temperature decreases gradually as shown in FIG. 3.

The cold heat quantity of salt water-mixed sherbet ice is defined as follows.

The cold heat quantity can be expressed in specific enthalpy [kcal/kg] of salt water-mixed sherbet ice as follows:

h=cw×(1−Ipf)×T+ci×Ipf×T−L×Ipf

in which h [kcal/kg] is the specific enthalpy of salt water-mixed sherbet ice, c is specific heat, T is the temperature of salt water-mixed sherbet ice, Ipf is the temperature of ice, and L is latent heat of solidification of water.

In this expression, the subscript w is designated as water and the subscript i is designated as ice.

When salt water is cooled, ice begins to be generated at the freezing point and the temperature decreases little by little while the amount of ice increases. The locus thereof varies according to the initial salt concentration and the state thereof is shown in FIG. 4. FIG. 4 shows states in salt concentrations of 1.0% to 4.5% taken at intervals of 0.5%. In FIG. 4, the abscissa axis shows enthalpy of salt water-mixed sherbet ice and the ordinate axis shows temperature. In FIG. 4, IPF % shows ice concentration.

For example, when salt water with a salt concentration of 3.5% is cooled from 0° C., it is cooled linearly. When the temperature reaches −2.1° C., salt water begins to be frozen and the temperature thereof decreases while the amount of ice increases. For example, when the ice concentration IPF of salt water-mixed sherbet ice is 30%, the temperature reaches −3.1° C. and the specific enthalpy reaches about −26 kcal/kg.

Next, a state in the case where fresh water is added to the salt water-mixed sherbet ice will be considered. When fresh water at a temperature of 0° C. or higher is added, the temperature of the salt water-mixed sherbet ice increases and the salt concentration of the salt water-mixed sherbet ice decreases because the temperature of the salt water-mixed sherbet ice is 0° C. or lower. Incidentally, a solution of ice mixed with salt water, such as salt water-mixed ice water or sherbet ice, has the property that the salt concentration thereof balances with the freezing point. Accordingly, when fresh water is added to salt water-mixed sherbet ice, part of ice in the salt water-mixed sherbet ice is melted so that the salt concentration of the salt water-mixed sherbet ice further decreases but the temperature of the salt water-mixed sherbet ice decreases. Consequently, the salt concentration of the salt water-mixed sherbet ice balances with the freezing point.

For example, when fresh water is injected into salt water-mixed sherbet ice having an ice concentration of 30% after the salt water-mixed sherbet ice is cooled to the ice concentration of 30% while produced with use of salt water having an initial salt concentration of 3.5%, the temperature of the salt water-mixed sherbet ice increases through the locus as shown in FIG. 4.

Incidentally, FIG. 4 shows states in the case where three kinds of fresh water at 0° C., 5° C. and 10° C. are injected into salt water-mixed sherbet ice in the condition that the amounts (weight ratios) of the added freshwater to the salt water-mixed sherbet ice are 5%, 10%, 20%, . . . , 100%.

FIG. 5 is a graph showing another example of ice-making curves in the case where the salt water-mixed sherbet ice is produced from salt water having a salt concentration of 2.5% by the steps ST204 to ST209 in the condition that the target point of finished salt water-mixed sherbet ice is −1.5° C. with an IPF of 25%.

Because the ice-maker 1 in Embodiment 1 can generate ice only when the initial salt concentration is 2.5% or higher as described above, a 2.5% line as a reference is shown in FIG. 5. As represented by the arrow in FIG. 5, ice is generated from salt water having a salt concentration of 2.5% until the IPF reaches an IPF (=35% in FIG. 5) higher by a predetermined value than the target IPF (=25% in FIG. 5). At the point of time when the IPF reaches the IPF (=35% in FIG. 5) higher by the predetermined value (the temperature of salt water-mixed sherbet ice reaches −2.2° C.), ice-making is stopped and fresh water at 0° C. is injected. It is found that salt water-mixed sherbet ice at a relatively high temperature as the target point of the target temperature (of −1.5° C. in FIG. 5) and the target IPF (of 25% in FIG. 5) can be obtained in this manner.

Although Embodiment 1 has been described upon the case where fresh water is injected so as to be mixed with salt water having a high salt concentration such as sea water, the aforementioned properties hold even when the fresh water is replaced with salt water. Even when thin salt water (salt water having a low salt concentration) is injected so as to be mixed with salt water having a high salt concentration such as sea water, it is possible to increase the temperature of salt water-mixed sherbet ice. However, the highest effect for increasing the temperature of salt water-mixed sherbet ice can be obtained when salt water having a salt concentration of 0, that is, fresh water is used.

In Embodiment 1, the drive source (rotary cylinder drive motor) 2 of the ice-maker 1 and the main circulating pump 11 can use a low-speed operating system or a variable-speed operating system in accordance with necessity.

Embodiment 2

Embodiment 2 of this invention will be described below with reference to FIGS. 6 to 8. FIG. 6 is a diagram showing another example of overall system configuration of the salt water-mixed sherbet ice producing apparatus for carrying out the salt water-mixed sherbet ice producing method. FIG. 7 is a flowchart showing an example of a salt water-mixed sherbet ice producing sequence in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 6. FIG. 8 is a graph showing an example of salt water state and ice-making curve in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus shown in FIG. 6.

Embodiment 2 is configured so that a dewatering process is added to the aforementioned Embodiment 1. Salt water-mixed sherbet ice having an ice concentration IPF higher than that in Embodiment 1 can be produced in Embodiment 2.

That is, as shown in FIG. 6, a dewatering unit composed of a dewatering pump 22, a dewatering pipe 221, a dewatering control valve 22 a and an integrating flowmeter 22 b is added to the apparatus shown in FIG. 1. As shown in FIG. 7, steps ST701 to ST705 are provided between the steps ST206 and ST207 in FIG. 2. The amount of water to be removed is calculated (step ST7O1). The stirrer 16 is stopped (step ST702). The dewatering pump 22 is operated (step ST703). The amount of water removed from salt water-mixed sherbet ice in the ice storage tank 14 is measured based on the output of the integrating flowmeter 22 b so that dewatering is stopped when the amount of water removed from the salt water-mixed sherbet ice reaches a predetermined value (step ST704). The stirrer 16 is restarted (step S705).

Incidentally, the steps ST701 to ST705 are executed by a dewatering function portion 103 of the controller 100.

According to Embodiment 2, it is found that salt water-mixed sherbet ice at a relatively high temperature of −1.5° C. with an ice concentration IPF of 30% which is higher than the ice concentration IPF of 25% in Embodiment 1 can be produced as follows. As represented by the arrow in FIG. 8, after ice is generated from salt water having a salt concentration of 2.5%, dewatering is slightly performed by the dewatering unit and then fresh water is injected or, in other words, water is removed from the salt water-mixed sherbet ice before the injection of fresh water.

Embodiment 3

Embodiment 3 of this invention will be described below with reference to FIGS. 9 and 10. FIG. 9 is a flow chart showing a further example of a salt water-mixed sherbet ice producing sequence in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing apparatus. FIG. 10 is a graph showing an example of salt water state and ice-making curve in the salt water-mixed sherbet ice producing method and the salt water-mixed sherbet ice producing sequence shown in FIG. 9.

Embodiment 3 is configured so that the ice-making and the injection of fresh water in Embodiment 1 are performed alternately and repeatedly. Salt water-mixed sherbet ice having an ice concentration IPF higher than that in Embodiment 1 can be produced in Embodiment 3 similarly to Embodiment 2.

In Embodiment 3, as shown in FIG. 9, the steps ST201 to ST206 are executed by a first standard ice-making function portion 101-1 of the controller 100. Then, steps ST701 to ST703 which are the same as the steps ST207 to ST209 are executed by a first fresh water injecting function portion 102-1. Then, steps ST704 to ST706 which are the same as the steps ST204 to ST206 are executed by a second standard ice-making function portion 101-2. Then, the steps ST207 to ST209 are executed by a second fresh water injecting function portion 102-2.

According to Embodiment 3, it is found that salt water-mixed sherbet ice having an ice concentration IPF higher than that in Embodiment 1 can be produced like Embodiment 2 in the following manner. As represented by the arrow in FIG. 10, ice-making and injection of fresh water are performed alternately and repeatedly several times.

Incidentally, in the case where salt water having a salt concentration of 3.0% is used by way of example, as shown in FIG. 11, salt water-mixed sherbet ice in a temperature range of −1.5° C. to −0.5° C. and an IPF range of 15% to 25% in a region surrounded by K-B-C-D-M can be produced in Embodiment 1 (without any dewatering unit) and Embodiment 3 (without any dewatering unit).

By one fresh water injecting cycle, the temperature and IPF of salt water-mixed sherbet ice can be adjusted in a region surrounded by E-C-F. By two fresh water injecting cycles and one ice-remaking cycle, the temperature and IPF of salt water-mixed sherbet ice can be adjusted in a region surrounded by G-C-D-H. By a plurality of fresh water injecting cycles and ice-remaking cycles, the temperature and IPF of salt water-mixed sherbet ice can be adjusted in a region surrounded by K-B-C-D-M.

The region surrounded by A-K-M is a region in which dewatering is essential. Unless the dewatering process in Embodiment 2 is provided, the temperature and IPF of salt water-mixed sherbet ice cannot be adjusted in the region surrounded by A-K-M.

As shown in FIG. 12, salt water-mixed sherbet ice in a temperature range of −1.5° C. to −0.5° C. and an IPF range of 15% to 25% in a region surrounded by A-B-C-D can be produced in Embodiment 2 (with a dewatering unit).

By one fresh water injecting cycle, the temperature and IPF of salt water-mixed sherbet ice can be adjusted in a region surrounded by E-C-F. By one dewatering and fresh water injecting cycle, the temperature and IPF of salt water-mixed sherbet ice can be adjusted in a region surrounded by A-B-C-D.

Incidentally, the term “salt water” used in Embodiments 1 to 3 means so-called salt water such as salt water obtained by mixing salt and water or sea water.

Although Embodiments 1 to 3 have been described upon the case where the injection of fresh water and dewatering are controlled by the controller 100 used commonly, the injection of fresh water and dewatering may be controlled by another controller provided separately from the controller 100. In this case, the controller can be easily added to the existing salt water-mixed sherbet ice producing apparatus.

In FIGS. 1 to 12, identical or equivalent parts are referred to by the same numerals. In Embodiments 2 and 3, description of parts identical or equivalent to those in Embodiment 1 is omitted as a rule.

Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this is not limited to the illustrative embodiments set forth herein. 

1. A method of producing salt water-mixed sherbet ice, comprising the steps of: generating salt water-mixed sherbet ice by cooling salt water fed to an ice-maker to generate ice, scraping the ice by scrapers to form small particles of ice to thereby mix the small particles of ice with the salt water; feeding the salt water-mixed sherbet ice from the ice-maker into an ice storage tank to thereby store the salt water-mixed sherbet ice in the ice storage tank; and storing a predetermined amount of the salt water-mixed sherbet ice with a predetermined sherbet concentration at a predetermined low temperature in the ice storage tank while the salt water-mixed sherbet ice stored in the ice storage tank is refluxed from the ice storage tank to the ice-maker repeatedly a plurality of times; wherein water is injected into the salt water-mixed sherbet ice in the process of producing salt water-mixed sherbet ice.
 2. A method of producing salt water-mixed sherbet ice according to claim 1, wherein the injection of water is performed in the ice storage tank.
 3. A method of producing salt water-mixed sherbet ice according to claim 2, wherein the injection of water is performed while the salt water-mixed sherbet ice in the ice storage tank is stirred.
 4. A method of producing salt water-mixed sherbet ice according to claim 1, wherein the formation of small particles of ice by the scrapers is stopped while the injection of water is performed.
 5. A method of producing salt water-mixed sherbet ice according to claim 3, wherein the formation of small particles of ice by the scrapers is stopped while the injection of water is performed.
 6. A method of producing salt water-mixed sherbet ice according to claim 1, wherein the formation of small particles of ice by the scrapers and the injection of water are performed alternately and repeatedly a plurality of times.
 7. A method of producing salt water-mixed sherbet ice according to claim 5, wherein the formation of small particles of ice by the scrapers and the injection of water are performed alternately and repeatedly a plurality of times.
 8. A method of producing salt water-mixed sherbet ice according to claim 1, wherein water is removed from the salt water-mixed sherbet ice before the injection of water.
 9. A method of producing salt water-mixed sherbet ice according to claim 7, wherein water is removed from the salt water-mixed sherbet ice before the injection of water.
 10. An apparatus of producing salt water-mixed sherbet ice, comprising: an ice-maker which generates salt water-mixed sherbet ice under control based on a controller in such a manner that ice generated by cooling salt water fed to the ice-maker is scraped by scrapers to form small particles of ice to thereby mix the small particles of ice with the salt water; an ice storage tank which stores the salt water-mixed sherbet ice fed from the ice-maker under control based on the controller; and a water injecting unit which injects water into the salt water-mixed sherbet ice; wherein control is performed by the controller so that the salt water-mixed sherbet ice stored in the ice storage tank is refluxed from the ice storage tank to the ice-maker and the injection of water is performed by the water injecting unit in steps of feeding the salt water-mixed sherbet ice from the ice-maker to the ice storage tank and refluxing the salt water-mixed sherbet ice from the ice storage tank to the ice-maker.
 11. An apparatus of producing salt water-mixed sherbet ice according to claim 10, wherein the injection of water is performed in the ice storage tank.
 12. An apparatus of producing salt water-mixed sherbet ice according to claim 11, further comprising a stirrer which stirs the salt water-mixed sherbet ice in the ice storage tank under control based on the controller, wherein the injection of water is performed while the salt water-mixed sherbet ice in the ice storage tank is stirred by the stirrer.
 13. An apparatus of producing salt water-mixed sherbet ice according to claim 10, wherein the formation of small particles of ice by the scrapers is stopped during the injection of water under control based on the controller.
 14. An apparatus of producing salt water-mixed sherbet ice according to claim 12, wherein the formation of small particles of ice by the scrapers is stopped during the injection of water under control based on the controller.
 15. An apparatus of producing salt water-mixed sherbet ice according to claim 10, wherein the formation of small particles of ice by the scrapers and the injection of water are performed alternately and repeatedly a plurality of times under control based on the controller.
 16. An apparatus of producing salt water-mixed sherbet ice according to claim 14, wherein the formation of small particles of ice by the scrapers and the injection of water are performed alternately and repeatedly a plurality of times under control based on the controller.
 17. An apparatus of producing salt water-mixed sherbet ice according to claim 10, further comprising a dewatering unit which removes water from the salt water-mixed sherbet ice, wherein the removal of water from the salt water-mixed sherbet ice is performed before the injection of water under control based on the controller.
 18. An apparatus of producing salt water-mixed sherbet ice according to claim 15, further comprising a dewatering unit which removes water from the salt water-mixed sherbet ice, wherein the removal of water from the salt water-mixed sherbet ice is performed before the injection of water under control based on the controller. 